Water-blocking high-adhesion packaging adhesive film for main-grid-free heterojunction and preparation method of water-blocking high-adhesion packaging adhesive film

Abstract

The invention relates to the field of packaging adhesive films, in particular to a packaging adhesive film for a water-blocking high-bonding-force junction type main-grid-free heterojunction and a preparation method of the packaging adhesive film. Comprising an outer water-blocking acid-absorbing layer and an inner bonding supporting layer, and the outer water-blocking acid-absorbing layer is prepared from, by mass, 100 parts of ethylene-vinyl acetate copolymer (EVA), 0.1-5 parts of antioxidant, 0.1-5 parts of silane coupling agent, 0.1-5 parts of free radical cross-linking agent, 0.1-5 parts of acid-absorbing agent and 0.1-5 parts of water-blocking agent; a water-blocking and acid-absorbing auxiliary agent is added into the outer-layer adhesive film, so that water vapor erosion and acetic acid decomposition can be reduced, the aging resistance of the assembly is effectively improved, and the reliability of the main-grid-free HJT battery is ensured; the adhesive force enhancing assistant is added into the inner-layer adhesive film, so that the adhesive force between the assembly and the main-grid-free HJT battery piece is improved, the situation that the adhesive film and the battery piece are easy to delaminate after high-temperature aging is effectively prevented, meanwhile, through irradiation treatment, the mobility is reduced, the coating effect on a welding strip is ensured, and thus the application of the main-grid-free HJT battery piece in the market is promoted.

Description

Technical Field

[0001] This invention relates to the field of encapsulation films, specifically to a water-resistant, high-adhesion encapsulation film for gateless heterojunctions and its preparation method. Background Technology

[0002] The long-term reliability of photovoltaic modules is highly dependent on the performance of the encapsulating film. As the core material between the solar cell and the glass, the encapsulating film performs multiple functions, including adhesion protection, light transmission assurance, and protection against environmental corrosion. With the photovoltaic industry moving towards higher efficiency and lower costs, busbarless technology (OBB / SMBB) has become the mainstream encapsulation solution for high-efficiency cells such as intrinsic thin-film heterojunction (HJT) cells and tunnel oxide contact (TOPCon) cells due to its ability to significantly reduce silver paste usage, minimize shading losses, and improve cell conversion efficiency.

[0003] However, the surface of the gridless HJT is a TCO (transparent conductive oxide) layer, rather than the silicon nitride layer of traditional silicon wafers. The difference in polarity leads to a decrease in its adhesion to conventional encapsulant films. At the same time, the absence of a grid results in an increased exposed area of ​​fine grid lines and more micro-gaps at the solder joint interface, making the cell more susceptible to water vapor penetration and electrochemical corrosion. This causes the electroluminescence (EL) of the cell to dim, accelerating the power decay of the module. Therefore, it is of great significance to prepare an HJT encapsulant film that is resistant to water vapor and corrosion, while improving the adhesion to the gridless HJT and preventing the encapsulant film from delaminating from the cell. Summary of the Invention

[0004] This invention provides a water-resistant, corrosion-resistant, and highly adhesive encapsulating film for a non-blocking, high-adhesion heterojunction without a main gate, which is used to solve at least one of the above-mentioned technical problems.

[0005] The technical solution adopted by this invention to solve its technical problem is: A water-resistant, highly adhesive encapsulating film for a gateless heterojunction, wherein the encapsulating film has a two-layer composite structure, comprising an outer water-resistant and acid-absorbing layer and an inner adhesive support layer. The outer water-blocking and acid-absorbing layer has the following composition by mass: 100 parts ethylene-vinyl acetate copolymer (EVA), 0.1-5 parts antioxidant, 0.1-5 parts silane coupling agent, 0.1-5 parts free radical crosslinking agent, 0.1-5 parts acid absorber, and 0.1-5 parts water-blocking agent. The inner adhesive support layer has the following composition by weight: 100 parts ethylene-vinyl acetate copolymer (EVA), 0.1-5 parts antioxidant, 0.1-5 parts silane coupling agent, 0.1-5 parts free radical crosslinking agent, and 0.1-5 parts adhesive strength enhancing agent. The inner layer adhesive film is used to fix the solder strips of the gridless heterojunction cell.

[0006] Furthermore, the preparation method of the adhesion-enhancing agent includes the following steps: 2-hydroxyethyl methacrylate is placed in a reaction apparatus and dehydrated under vacuum at 60°C. Then, under a nitrogen protective atmosphere, phosphorus pentoxide with a molar ratio of 1:4 to 2-hydroxyethyl methacrylate and 0.01% polymerization inhibitor are added. After the reaction is completed, the mixture is cooled to 25°C, and the resulting pale yellow liquid is the agent.

[0007] Furthermore, the preparation method of the water-blocking agent is as follows: Montmorillonite and diatomaceous earth are prepared into a mixture in a ratio of 1:2, and then the mixture is stirred with the hydrolysis product of γ-aminopropyltriethoxysilane in a ratio of 1:3 at 60°C for 2 hours, and then cured at 110°C to obtain the product.

[0008] Furthermore, the matrix resin is EVA resin, wherein the vinyl acetate (VA) content in the EVA resin is 26-30%, and the melt flow rate is 15-25 g / 10 min.

[0009] Furthermore, the free radical crosslinking agent includes any one or a combination of several of the following: tert-butyl peroxycarbonate-2-ethylhexyl ester, 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane, 1,1-bis(tert-pentyl peroxy)-3,3,5-trimethylcyclohexane, tert-pentyl peroxycarbonate, tert-butyl peroxy3,3,5-trimethylhexanoate, and tert-pentyl peroxy2-ethylhexyl carbonate.

[0010] Furthermore, the antioxidant includes any one or more of antioxidant 1790, antioxidant 1726, antioxidant 1076, antioxidant 1010, antioxidant 1098, and antioxidant 245.

[0011] Furthermore, the silane coupling agent includes any one or a combination of several of 3-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and γ-aminopropyltriethoxysilane.

[0012] Furthermore, the acid absorbent includes any one or a combination of several of magnesium hydroxide, calcium hydroxide, magnesium oxide, calcium oxide, magnesium carbonate, and calcium carbonate.

[0013] Another objective of this invention is to provide a method for preparing a water-resistant, corrosion-resistant, and highly adhesive encapsulating film for a non-blocking, high-adhesion heterojunction without a main gate.

[0014] A method for preparing a water-resistant, high-adhesion encapsulating film for a gateless heterojunction, the method comprising the following steps: The encapsulating film is prepared by high-speed mixing of EVA resin, antioxidant, acid scavenger, silane coupling agent, free radical crosslinking agent, adhesion enhancer and water barrier agent, and co-extrusion casting through a twin-screw extruder at a temperature of 80±5℃ and a screw speed of 15r / min.

[0015] The beneficial effects of this invention are as follows: Employing a multi-layered structural design, this system achieves multiple functionalities. The outer layer of the encapsulant incorporates water-blocking and acid-absorbing agents to reduce moisture erosion and acetic acid decomposition, effectively improving the module's aging resistance and ensuring the reliability of the busbarless HJT cell. The inner layer of the encapsulant incorporates adhesion-enhancing agents to improve the adhesion between the module and the busbarless HJT cell, effectively preventing delamination after high-temperature aging. Furthermore, irradiation treatment reduces fluidity, ensuring effective coating of the solder ribbon, thus promoting the market application of busbarless HJT cells. Detailed Implementation

[0016] The technical solution of the present invention will be clearly and completely described below with the aid of embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] This invention provides a water-resistant, corrosion-resistant, and highly adhesive encapsulating film for a non-blocking, high-adhesion heterojunction without a main grid. It is prepared by co-extrusion using a twin-screw extruder. The film structure is designed as a two-layer composite structure, including an outer water-blocking and acid-absorbing layer and an inner adhesive support layer. The outer water-blocking and acid-absorbing layer has the following composition by mass: 100 parts ethylene-vinyl acetate copolymer (EVA), 0.1-5 parts antioxidant, 0.1-5 parts silane coupling agent, 0.1-5 parts free radical crosslinking agent, 0.1-5 parts acid absorber, and 0.1-5 parts water-blocking agent. The composition of the inner adhesive support layer by weight is as follows: 100 parts ethylene-vinyl acetate copolymer (EVA), 0.1-5 parts antioxidant, 0.1-5 parts silane coupling agent, 0.1-5 parts free radical crosslinking agent, and 0.1-5 parts adhesive strength enhancing agent. The inner layer film needs to be treated by irradiation to fix the gridless HJT welding strip. The process parameters are: vehicle speed 1-30 and irradiation energy 10kGy-50kGy.

[0018] Among them, the EVA resin is one or more of the following: UE2828 type EVA resin produced by Taiwan Plastics Research Institute, V6610M of Yangzi Petrochemical, and E280PV type EVA resin produced by Hanwha Total, wherein the mass percentage of vinyl acetate is 26-30%.

[0019] The encapsulating film for the water-resistant, high-adhesion, gridless heterojunction cell in this application adopts a multi-layer structure design to achieve multi-functional effects. The outer film contains water-resistant and acid-absorbing additives, which can reduce water vapor erosion and acetic acid decomposition, effectively improving the aging resistance of the module and ensuring the reliability of the gridless HJT cell. The inner film contains adhesion-enhancing additives, which improves the adhesion between the module and the gridless HJT cell, effectively preventing the film and cell from easily delaminating after high-temperature aging. At the same time, the irradiation treatment reduces fluidity and ensures the coating effect of the solder ribbon, thereby promoting the application of gridless HJT cells in the market.

[0020] Example 1 A water-resistant, highly adhesive encapsulating film for gateless heterojunctions is disclosed. This encapsulating film has a two-layer composite structure, comprising an outer water-resistant and acid-absorbing layer and an inner adhesive support layer. The outer water-blocking and acid-absorbing layer is composed of the following components by weight: 100 parts ethylene-vinyl acetate copolymer (EVA), 0.5 parts antioxidant tris(2,4-di-tert-butylphenyl) phosphate, 0.5 parts silane coupling agent vinyltriethoxysilane, 0.8 parts free radical crosslinking agent tert-butylperoxycarbonate-2-ethylhexyl ester, 0.5 parts acid absorber magnesium hydroxide, and 0.5 parts silane-modified water-blocking agent. The composition of the inner adhesive support layer is as follows: by weight, 100 parts of ethylene-vinyl acetate copolymer (EVA), 0.5 parts of antioxidant tris(2,4-di-tert-butylphenyl) phosphate, 0.5 parts of silane coupling agent vinyltriethoxysilane, 0.8 parts of free radical crosslinking agent tert-butylperoxycarbonate-2-ethylhexyl ester, and 0.5 parts of adhesive strength enhancing agent phosphate-modified acrylate; The inner layer of adhesive film is used to fix the solder strips of gridless heterojunction cells.

[0021] The preparation method of the adhesion-enhancing agent includes the following steps: 2-hydroxyethyl methacrylate is placed in a reaction apparatus and dehydrated under vacuum at 60°C. Then, under a nitrogen protective atmosphere, phosphorus pentoxide with a molar ratio of 1:4 to 2-hydroxyethyl methacrylate and 0.01% polymerization inhibitor are added. After the reaction is completed, the mixture is cooled to 25°C, and the resulting pale yellow liquid is the agent.

[0022] The water-blocking agent is prepared as follows: the hydrolysis products of montmorillonite and γ-aminopropyltriethoxysilane are mixed at a ratio of 1:3 and stirred at 60°C for 2 hours, and then cured at 110°C to obtain the product.

[0023] The EVA resin contains 26% vinyl acetate (VA) and has a melt flow rate of 15 g / 10 min.

[0024] The raw materials for the water-blocking and acid-absorbing layer and the adhesive support layer are mixed separately and then added to a twin-screw extruder. The extruded materials of the water-blocking and acid-absorbing layer and the adhesive support layer are melted and plasticized before being injected into the same die. They merge within the die to form a single melt flow. A double-layer composite photovoltaic co-extruded film is prepared through processes such as melt extrusion, casting, cooling, slitting, and winding. After irradiation treatment with 30 kGy energy (denoted as A1), the thickness of the water-blocking and acid-absorbing layer is calculated to be 0.4 mm using microscopic metallographic testing, and the thickness of the adhesive support layer is 0.1 mm.

[0025] Example 2 A water-resistant, highly adhesive encapsulating film for gateless heterojunctions is disclosed. This encapsulating film has a two-layer composite structure, comprising an outer water-resistant and acid-absorbing layer and an inner adhesive support layer. Raw materials for the outer water-blocking and acid-absorbing layer: by weight, 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 0.5 parts antioxidant β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl alcohol ester, 0.5 parts silane coupling agent vinyltrimethoxysilane, 0.5 parts acid absorber calcium hydroxide, and 0.5 parts silane-modified water-blocking agent.

[0026] Raw materials for the inner adhesive support layer: by weight, 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, 0.5 parts antioxidant β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl alcohol ester, 0.5 parts silane coupling agent vinyltrimethoxysilane, and 0.5 parts adhesive strength enhancing agent phosphate-modified acrylate; The inner layer of adhesive film is used to fix the solder strips of gridless heterojunction cells.

[0027] The preparation method of the adhesion-enhancing agent includes the following steps: 2-hydroxyethyl methacrylate is placed in a reaction apparatus and dehydrated under vacuum at 60°C. Then, under a nitrogen protective atmosphere, phosphorus pentoxide with a molar ratio of 1:4 to 2-hydroxyethyl methacrylate and 0.01% polymerization inhibitor are added. After the reaction is completed, the mixture is cooled to 25°C, and the resulting pale yellow liquid is the agent.

[0028] The water-blocking agent is prepared as follows: the hydrolysis products of kaolin and γ-aminopropyltriethoxysilane are stirred at 60°C for 2 hours in a ratio of 1:3, and then cured at 110°C to obtain the product.

[0029] Among them, the EVA resin has a vinyl acetate (VA) content of 28% and a melt flow rate of 15g / 10min.

[0030] The raw materials for the water-blocking and acid-absorbing layer and the adhesive support layer are mixed separately and then added to a twin-screw extruder. The extruded materials of the water-blocking and acid-absorbing layer and the adhesive support layer are melted and plasticized before being injected into the same die. They merge within the die to form a single melt flow. A double-layer composite photovoltaic co-extruded film is prepared through processes such as melt extrusion, casting, cooling, slitting, and winding. After irradiation treatment with 30 kGy energy (denoted as A2), the thickness of the water-blocking and acid-absorbing layer is calculated to be 0.3 mm using microscopic metallographic testing, and the thickness of the adhesive support layer is 0.2 mm.

[0031] Example 3 A water-resistant, highly adhesive encapsulating film for gateless heterojunctions is disclosed. This encapsulating film has a two-layer composite structure, comprising an outer water-resistant and acid-absorbing layer and an inner adhesive support layer. The raw materials for the outer water-blocking and acid-absorbing layer are as follows (by weight): 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent 1,1-bis(tert-amylperoxy)-3,3,5-trimethylcyclohexane, 0.5 parts antioxidant tris(4-nonylphenol) phosphite, 0.5 parts silane coupling agent vinyltriperoxide tert-butylsilane, 0.5 parts acid-absorbing agent magnesium oxide, and 0.5 parts silane-modified water-blocking agent.

[0032] The raw materials for the inner adhesive support layer are as follows: by weight, 100 parts of ethylene-vinyl acetate copolymer (EVA), 0.8 parts of free radical crosslinking agent 1,1-bis(tert-amylperoxy)-3,3,5-trimethylcyclohexane, 0.5 parts of antioxidant tris(4-nonylphenol) phosphite, 0.5 parts of silane coupling agent vinyltriperoxide tert-butylsilane, and 0.5 parts of adhesive strength enhancing agent phosphate-modified acrylate.

[0033] The inner layer of adhesive film is used to fix the solder strips of gridless heterojunction cells.

[0034] The preparation method of the adhesion-enhancing agent includes the following steps: 2-hydroxyethyl methacrylate is placed in a reaction apparatus and dehydrated under vacuum at 60°C. Then, under a nitrogen protective atmosphere, phosphorus pentoxide with a molar ratio of 1:4 to 2-hydroxyethyl methacrylate and a polymerization inhibitor are added. After the reaction is completed, the mixture is cooled to 25°C, and the resulting pale yellow liquid is the agent.

[0035] The water-blocking agent is prepared as follows: the hydrolysis products of diatomaceous earth and γ-aminopropyltriethoxysilane are mixed at a ratio of 1:3 and stirred at 60°C for 2 hours, and then cured at 110°C to obtain the product.

[0036] Among them, the EVA resin has a vinyl acetate (VA) content of 28% and a melt flow rate of 15g / 10min.

[0037] The raw materials for the water-blocking and acid-absorbing layer and the adhesive support layer are mixed separately and then added to a twin-screw extruder. The extruded materials of the water-blocking and acid-absorbing layer and the adhesive support layer are melted and plasticized before being injected into the same die. They merge within the die to form a single melt flow. A double-layer composite photovoltaic co-extruded film is prepared through processes such as melt extrusion, casting, cooling, slitting, and winding. After irradiation treatment with 30 kGy energy (denoted as A3), the thickness of the water-blocking and acid-absorbing layer is calculated to be 0.2 mm, and the thickness of the adhesive support layer is 0.3 mm.

[0038] Example 4 A water-resistant, highly adhesive encapsulating film for gateless heterojunctions is disclosed. This encapsulating film has a two-layer composite structure, comprising an outer water-resistant and acid-absorbing layer and an inner adhesive support layer. Raw materials for the outer water-blocking and acid-absorbing layer: by weight, 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent tert-amyl peroxide carbonate, 0.5 parts antioxidant tris(2,4-di-tert-butylphenyl) phosphate, 0.5 parts silane coupling agent vinyltriethoxysilane, 0.5 parts acid absorber calcium oxide, and 0.5 parts silane-modified water-blocking agent.

[0039] The raw materials of the inner adhesive support layer are as follows (by weight): 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent tert-amyl peroxide carbonate, 0.5 parts antioxidant tris(2,4-di-tert-butylphenyl) phosphate, 0.5 parts silane coupling agent vinyltriethoxysilane, and 1 part adhesive strength enhancing agent phosphate-modified acrylate. The inner layer of adhesive film is used to fix the solder strips of gridless heterojunction cells.

[0040] The preparation method of the adhesion-enhancing agent includes the following steps: 2-hydroxyethyl methacrylate is placed in a reaction apparatus and dehydrated under vacuum at 60°C. Then, under a nitrogen protective atmosphere, phosphorus pentoxide with a molar ratio of 1:4 to 2-hydroxyethyl methacrylate and a polymerization inhibitor are added. After the reaction is completed, the mixture is cooled to 25°C, and the resulting pale yellow liquid is the agent.

[0041] The water-blocking agent is prepared as follows: talc powder and the hydrolysis product of γ-aminopropyltriethoxysilane are mixed at a ratio of 1:3 and stirred at 60°C for 2 hours, followed by curing at 110°C to obtain the product.

[0042] Among them, the EVA resin has a vinyl acetate (VA) content of 28% and a melt flow rate of 15g / 10min.

[0043] The raw materials for the water-blocking and acid-absorbing layer and the adhesive support layer are mixed separately and then added to a twin-screw extruder. The extruded materials of the water-blocking and acid-absorbing layer and the adhesive support layer are melted and plasticized before being injected into the same die. They merge within the die to form a single melt flow. A double-layer composite photovoltaic co-extruded film is prepared through processes such as melt extrusion, casting, cooling, slitting, and winding. After irradiation treatment with 30 kGy energy (denoted as A4), the thickness of the water-blocking and acid-absorbing layer is calculated to be 0.4 mm using microscopic metallographic testing, and the thickness of the adhesive support layer is 0.1 mm.

[0044] Example 5 A water-resistant, highly adhesive encapsulating film for gateless heterojunctions is disclosed. This encapsulating film has a two-layer composite structure, comprising an outer water-resistant and acid-absorbing layer and an inner adhesive support layer. Raw materials for the outer water-blocking and acid-absorbing layer: by weight, 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent tert-butyl peroxide 3,3,5-trimethylhexanoate, 0.5 parts antioxidant pentaerythritol diacetyl phosphite, 0.5 parts silane coupling agent vinyltris(β-methoxyethoxy)silane, 0.5 parts acid absorber magnesium carbonate, and 1.5 parts silane-modified water-blocking agent.

[0045] The raw materials of the inner adhesive support layer are as follows (by weight): 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent tert-butyl peroxide 3,3,5-trimethylhexanoate, 0.5 parts antioxidant pentaerythritol diphosphite dioctadecyl ester, 0.5 parts silane coupling agent vinyltris(β-methoxyethoxy)silane, and 1.5 parts adhesive strength enhancing agent phosphate-modified acrylate. The inner layer of adhesive film is used to fix the solder strips of gridless heterojunction cells.

[0046] The preparation method of the adhesion-enhancing agent includes the following steps: 2-hydroxyethyl methacrylate is placed in a reaction apparatus and dehydrated under vacuum at 60°C. Then, under a nitrogen protective atmosphere, phosphorus pentoxide with a molar ratio of 1:4 to 2-hydroxyethyl methacrylate and 0.01% polymerization inhibitor are added. After the reaction is completed, the mixture is cooled to 25°C, and the resulting pale yellow liquid is the agent.

[0047] The water-blocking agent is prepared as follows: Feldspar powder and the hydrolysis product of γ-aminopropyltriethoxysilane are mixed at a ratio of 1:3 and stirred at 60°C for 2 hours, and then cured at 110°C to obtain the product.

[0048] The EVA resin contains 28% vinyl acetate (VA) and has a melt flow rate of 15 g / 10 min.

[0049] The raw materials for the water-blocking and acid-absorbing layer and the adhesive support layer are mixed separately and then added to a twin-screw extruder. The extruded materials of the water-blocking and acid-absorbing layer and the adhesive support layer are melted and plasticized before being injected into the same die. They merge within the die to form a single melt flow. A double-layer composite photovoltaic co-extruded film is prepared through processes such as melt extrusion, casting, cooling, slitting, and winding. After irradiation treatment with 30 kGy energy (designated A5), the thickness of the water-blocking and acid-absorbing layer is calculated to be 0.4 mm, and the thickness of the adhesive support layer is 0.1 mm.

[0050] Comparative Example 1 A water-resistant, highly adhesive encapsulating film for gateless heterojunctions is disclosed. This encapsulating film has a two-layer composite structure, comprising an outer water-resistant and acid-absorbing layer and an inner adhesive support layer. The raw materials for the outer water-blocking and acid-absorbing layer are as follows (by weight): 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent tert-butyl percarbonate-2-ethylhexyl ester, 0.5 parts antioxidant tris(2,4-di-tert-butylphenyl) phosphate, 0.5 parts silane coupling agent vinyltriethoxysilane, and 0.5 parts acid absorber magnesium hydroxide.

[0051] The raw materials of the inner adhesive support layer are as follows (by weight): 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent tert-butyl percarbonate-2-ethylhexyl ester, 0.5 parts antioxidant tris(2,4-di-tert-butylphenyl) phosphate, and 0.5 parts silane coupling agent vinyltriethoxysilane.

[0052] The raw materials for the water-blocking and acid-absorbing layer and the adhesive support layer are mixed separately and then added to a twin-screw extruder. The extruded materials of the water-blocking and acid-absorbing layer and the adhesive support layer are melted and plasticized before being injected into the same die. They merge within the die to form a single melt flow. A double-layer composite photovoltaic co-extruded film is prepared through processes such as melt extrusion, casting, cooling, slitting, and winding. After irradiation treatment with 30 kGy energy (denoted as B1), the thickness of the water-blocking and acid-absorbing layer is calculated to be 0.4 mm, and the thickness of the adhesive support layer is 0.1 mm.

[0053] Comparative Example 2 A water-resistant, highly adhesive encapsulating film for gateless heterojunctions is disclosed. This encapsulating film has a two-layer composite structure, comprising an outer water-resistant and acid-absorbing layer and an inner adhesive support layer. Raw materials for the outer water-blocking and acid-absorbing layer: by weight, 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent tert-butyl percarbonate-2-ethylhexyl ester, 0.5 parts antioxidant tris(2,4-di-tert-butylphenyl) phosphate, 0.5 parts silane coupling agent vinyltriethoxysilane, 0.5 parts acid absorber magnesium hydroxide, and 0.5 parts silane-modified water-blocking agent.

[0054] The raw materials of the inner adhesive support layer are as follows (by weight): 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent tert-butyl percarbonate-2-ethylhexyl ester, 0.5 parts antioxidant tris(2,4-di-tert-butylphenyl) phosphate, and 0.5 parts silane coupling agent vinyltriethoxysilane.

[0055] The water-blocking agent is prepared as follows: the hydrolysis products of montmorillonite and γ-aminopropyltriethoxysilane are mixed at a ratio of 1:3 and stirred at 60°C for 2 hours, and then cured at 110°C to obtain the product.

[0056] The raw materials for the water-blocking and acid-absorbing layer and the adhesive support layer are mixed separately and then added to a twin-screw extruder. The extruded materials of the water-blocking and acid-absorbing layer and the adhesive support layer are melted and plasticized before being injected into the same die. They merge within the die to form a single melt flow. A double-layer composite photovoltaic co-extruded film is prepared through processes such as melt extrusion, casting, cooling, slitting, and winding. After irradiation treatment with 30 kGy energy (denoted as B2), the thickness of the water-blocking and acid-absorbing layer is calculated to be 0.4 mm, and the thickness of the adhesive support layer is 0.1 mm.

[0057] Comparative Example 3 A water-resistant, highly adhesive encapsulating film for gateless heterojunctions is disclosed. This encapsulating film has a two-layer composite structure, comprising an outer water-resistant and acid-absorbing layer and an inner adhesive support layer. The raw materials for the outer water-blocking and acid-absorbing layer are as follows (by weight): 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent tert-butyl percarbonate-2-ethylhexyl ester, 0.5 parts antioxidant tris(2,4-di-tert-butylphenyl) phosphate, 0.5 parts silane coupling agent vinyltriethoxysilane, and 0.5 parts acid absorber magnesium hydroxide.

[0058] The raw materials of the inner adhesive support layer are as follows (by weight): 100 parts ethylene-vinyl acetate copolymer (EVA), 0.8 parts free radical crosslinking agent tert-butyl percarbonate-2-ethylhexyl ester, 0.5 parts antioxidant tris(2,4-di-tert-butylphenyl) phosphate, 0.5 parts silane coupling agent vinyltriethoxysilane, and 1.5 parts adhesive strength enhancing agent phosphate-modified acrylate.

[0059] The raw materials for the water-blocking and acid-absorbing layer and the adhesive support layer are mixed separately and then added to a twin-screw extruder. The extruded materials of the water-blocking and acid-absorbing layer and the adhesive support layer are melted and plasticized before being injected into the same die. They merge within the die to form a single melt flow. A double-layer composite photovoltaic co-extruded film is prepared through processes such as melt extrusion, casting, cooling, slitting, and winding. After irradiation treatment with 30 kGy energy (designated B3), the thickness of the water-blocking and acid-absorbing layer is calculated to be 0.4 mm, and the thickness of the adhesive support layer is 0.1 mm.

[0060] Performance testing The encapsulating films obtained through the above embodiments and comparative examples were evaluated using the following test methods, and the evaluation results are listed in the table below.

[0061] 1. Appearance evaluation of cell corrosion in the module: Single-glass module encapsulation test was conducted using the encapsulation films of Examples 1-5 and Comparative Examples 1-3. The cells were placed in the laminator in the order of glass / encapsulation film / cell / encapsulation film / backsheet and laminated at 145℃ (vacuuming for 6 min, lamination for 10 min) to obtain the single-glass module. The module was then subjected to PCT aging (121℃, 100%RH), and the appearance corrosion of the cell was observed by electroluminescence (EL) tracking.

[0062] 2. Gridless HJT / Encapsulation Film: Take 3mm glass, encapsulation film, TPT backplane, heterojunction solar cell, and high-temperature cloth, and place them in a vacuum laminator in the order of glass / encapsulation film / solar cell / high-temperature cloth / backplane. Laminate at 145℃ for 15 minutes. The test is conducted according to GB / T2790-1995, using a tensile testing machine at a speed of 100mm / min. Record the bond strength values ​​of the solar cell and encapsulation film.

[0063] 3. Glass / Encapsulating Film Bond Strength Test: Take 3mm thick glass, encapsulating film, and TPT backsheet, and place them in a vacuum laminator in the order of glass / encapsulating film / backsheet. Laminate at 145℃ for 15 minutes. The test is conducted according to GB / T2790-1995, using a tensile testing machine at a speed of 100mm / min. Record the bond strength values ​​of the glass and the encapsulating film.

[0064] 4. The water vapor transmission rate test method refers to standard GB / T29848 "Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic module encapsulation" Table 1: Test results of packaging materials in Examples 1-5 and Comparative Examples 1-3 Based on the comparison of the water vapor transmission rate and EL test results after PCT aging between the above embodiments and comparative examples, it can be seen that the modules encapsulated with the film of the comparative example group using the present invention showed obvious corrosion at the edges of the solar cells after PCT 96h and PCT 144h aging; while after introducing the modified water-absorbing material into the encapsulation material system, no corrosion was observed at the edges of the solar cells of the modules encapsulated with the film of the embodiment group under the same aging conditions. Furthermore, after simultaneously adding an adhesion-enhancing agent, all performance indicators of the embodiments of the present invention are significantly better than those of the conventional formulation comparative example B1.

[0065] In summary, the introduction of modified water-absorbing materials can effectively block moisture from corroding the adhesive film and improve the reliability of the module under aging conditions; while the addition of adhesion-enhancing additives significantly enhances the adhesion strength between the adhesive film and the HJT solar cell, and also improves the corrosion resistance of the solar cell to a certain extent.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-resistant, high-adhesion encapsulating film for a gateless heterojunction, characterized in that: The encapsulating film has a double-layer composite structure, including an outer water-blocking and acid-absorbing layer and an inner adhesive and support layer. The outer water-blocking and acid-absorbing layer has the following composition by mass: 100 parts ethylene-vinyl acetate copolymer (EVA), 0.1-5 parts antioxidant, 0.1-5 parts silane coupling agent, 0.1-5 parts free radical crosslinking agent, 0.1-5 parts acid absorber, and 0.1-5 parts water-blocking agent. The inner adhesive support layer has the following composition by weight: 100 parts ethylene-vinyl acetate copolymer (EVA), 0.1-5 parts antioxidant, 0.1-5 parts silane coupling agent, 0.1-5 parts free radical crosslinking agent, and 0.1-5 parts adhesive strength enhancing agent. The inner layer adhesive film is used to fix the solder strips of the gridless heterojunction cell.

2. The encapsulating film for a water-blocking, high-adhesion, gridless heterojunction according to claim 1, characterized in that: The preparation method of the adhesion-enhancing agent includes the following steps: 2-hydroxyethyl methacrylate is placed in a reaction apparatus and dehydrated under vacuum at 60°C. Then, under a nitrogen protective atmosphere, phosphorus pentoxide and 0.01% polymerization inhibitor are added in a molar ratio of 1:4 to 2-hydroxyethyl methacrylate. After the reaction is completed, the mixture is cooled to 25°C, and the resulting pale yellow liquid is the agent.

3. The encapsulating film for a water-blocking, high-adhesion, gridless heterojunction according to claim 1, characterized in that: The water-blocking agent is prepared as follows: one or more of montmorillonite, kaolin, diatomite, talc powder, feldspar powder, etc., are mixed with the hydrolysis product of γ-aminopropyltriethoxysilane in a ratio of 1:3, stirred at 60°C for 2 hours, and then cured at 110°C to obtain the product.

4. The encapsulating film for a water-blocking, high-adhesion, gridless heterojunction according to claim 1, characterized in that: The matrix resin is EVA resin, and the EVA resin contains 26-30% vinyl acetate (VA) and has a melt flow rate of 15-25 g / 10 min.

5. The encapsulating film for a water-blocking, high-adhesion, gridless heterojunction according to claim 1, characterized in that: The free radical crosslinking agent includes any one or a combination of several of the following: tert-butyl peroxycarbonate-2-ethylhexyl ester, 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane, 1,1-bis(tert-pentyl peroxy)-3,3,5-trimethylcyclohexane, tert-pentyl peroxycarbonate, tert-butyl peroxy3,3,5-trimethylhexanoate, and tert-pentyl peroxy2-ethylhexyl carbonate.

6. The encapsulating film for a water-blocking, high-adhesion, gridless heterojunction according to claim 1, characterized in that: The antioxidants include any one or more of antioxidants 1790, 1726, 1076, 1010, 1098, and 245.

7. The encapsulating film for a water-blocking, high-adhesion, gridless heterojunction according to claim 1, characterized in that: The silane coupling agent includes any one or a combination of several of 3-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and γ-aminopropyltriethoxysilane.

8. The water-blocking, high-adhesion, gridless heterojunction encapsulating film according to claim 1, characterized in that: The acid absorbent includes any one or a combination of several of magnesium hydroxide, calcium hydroxide, magnesium oxide, calcium oxide, magnesium carbonate, and calcium carbonate.

9. A method for preparing a water-resistant, high-adhesion encapsulating film for a gateless heterojunction as described in any one of claims 1-9, characterized in that: The preparation method includes the following steps: The encapsulating film is prepared by high-speed mixing of EVA resin, antioxidant, acid scavenger, silane coupling agent, free radical crosslinking agent, adhesion enhancer and water barrier agent, and co-extrusion casting through a twin-screw extruder at a temperature of 80±5℃ and a screw speed of 15r / min.

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